In the case of such machines, which are known in practice (e.g. Contiform of the firm of Krones AG), the rotor of the blowing module and the conveyor of the heating module are driven in common through a main drive which is normally associated with the blowing module, since the blowing module has higher power requirements. When setting or retooling the machine, or when a failure occurred either in the heating module or in the blowing module, work has to be done in a clocked mode in the blowing module and/or in the heating module. During retooling or setting operations it will, for example, be necessary to exchange or convert molds in the blowing module and to exchange fittings, such as preform grippers, shielding plates and the like, in the heating module. In the course of such operations, the rotor in the blowing module will often have to be positioned at locations which are different from those of the conveyor in the heating module. This is one of the reasons for the fact that such work at the blowing module and at the heating module is carried out with a time shift, since, in view of the necessity of positioning the respective components at different locations, the operators would otherwise impede one another. In addition, the operational risk would be high, if the operators worked simultaneously at both modules and if they mutually endangered one another during the respective stepwise advance. Another drawback of the known principle is to be seen in the fact that, if a malfunction should, for example, occur in a further unit supplied by the blowing module, e.g. a blockage in a downstream filler, both the rotor in the blowing module and the conveyor in the heating module will have to be stopped until the blockage has been eliminated. The preforms in the heating module may be damaged when the conveyor stands still so that, subsequently, time-consuming resetting operations will become necessary. In addition, the main drive will unnecessarily waste power in the clocked mode of operation, when said main drive also moves the conveyor while work is being done in the blowing module or when the main drive also drives the rotor while work is being done in the heating module. The most serious drawback is, however, that the setting or retooling periods and, consequently, the downtimes of the machine are, in total, inexpediently long.